"Peer review" (or "refereed") means that an article is reviewed by experts in that field before the article gets published. This means that if a scientist writes an article on stem cells, other experts on stem cells will review the article to make sure it’s of high enough quality to be published. The peer review (or referee) process ensures that the research described in a journal's articles is sound and of high quality.
Many databases available through GALILEO give you the option to search for only peer reviewed items.
You can search in Ulrich's Periodicals Directory (Ulrichsweb) to see if the article is Refereed (Peer Reviewed).
Some databases will tell you if the article is in a peer-reviewed journal.
Journal Title Information: